Idempotency is not an optimization. Idempotency is a promise.

When a system claims idempotency, it commits to a contract of sameness under repetition.

I. The Misuse of the Word “Idempotent”

Many systems label operations idempotent because:

retries happen

networks duplicate messages

clients repeat requests

This treats idempotency as tolerance.

That is incorrect.

Idempotency is obligation.

II. Idempotency Defines Legal Equivalence

To be idempotent means:

one execution equals many executions

outcomes are identical

side effects do not multiply

state converges deterministically

If repetition changes reality, the contract is broken.

III. Idempotency Is Contextual Law

Idempotency is not global.

An operation may be idempotent:

within a time window

within a version

within a scope

within a declared key

Outside that context, the promise does not apply.

Undeclared scope is false idempotency.

IV. Idempotency Requires Identity

Idempotency without identity is impossible.

The system must know:

what is being repeated

which intent this corresponds to

why two requests are equivalent

Idempotency keys are not hints. They are legal identifiers.

V. Silent Deduplication Is Illegal

When a system silently collapses duplicates:

intent is erased

attempts disappear

accountability is lost

Deduplication without record rewrites history.

That is unlawful.

VI. Idempotency Must Be Recorded

A lawful idempotent system:

records first execution

records subsequent equivalents

links them under the same intent

preserves attempt history

Equivalence does not mean invisibility.

VII. Idempotency Must Be Replayable

Replay must show:

the original execution

every equivalent repetition

the same final state

If replay produces different effects depending on execution count, the contract fails.

VIII. Infrastructure Idempotency Is Not Enough

HTTP PUT semantics, message de-duplication, and database constraints do not define law.

They enforce mechanics.

Idempotency law must live in:

kernel

intent model

policy registry

Not in clients.

IX. Final Conclusion

Idempotency is a contract.

A lawful system:

declares idempotency explicitly

defines scope and identity

records all attempts

guarantees deterministic equivalence

replays idempotency faithfully

Anything else allows repetition to alter reality while claiming sameness.

Idempotency Is a Contract